Helmet

ABSTRACT

A helmet ( 10 ) comprising: an airbag ( 1 ) having an airbag wall surrounding an internal cavity; and one or more tensional reinforcements ( 2 ) extending through the internal cavity between different points on the airbag wall.

The present invention relates helmets. In particular, the inventionrelates to the provision of a helmet with an airbag that hasreinforcements.

Helmets are known for use in various activities. These activitiesinclude combat and industrial purposes, such as protective helmets forsoldiers and hard-hats or helmets used by builders, mine-workers, oroperators of industrial machinery for example. Helmets are also commonin sporting activities. For example, protective helmets are used in icehockey, cycling, motorcycling, motor-car racing, skiing, snow-boarding,skating, skateboarding, equestrian activities, American football,baseball, rugby, cricket, lacrosse, climbing, airsoft and paintballing.

Helmets can be of fixed size or adjustable, to fit different sizes andshapes of head. In some types of helmet, e.g. commonly in ice-hockeyhelmets, the adjustability can be provided by moving parts of the helmetto change the outer and inner dimensions of the helmet. This can beachieved by having a helmet with two or more parts which can move withrespect to each other. In other cases, e.g. commonly in cycling helmets,the helmet is provided with an attachment device for fixing the helmetto the user's head, and it is the attachment device that can vary indimension to fit the user's head whilst the main body or shell of thehelmet remains the same size. Combinations of these adjustmentmechanisms are also possible.

Helmets are often made of an outer shell, that is usually hard and madeof a plastic or a composite material, and an energy absorbing layercalled a liner. Nowadays, a protective helmet has to be designed so asto satisfy certain legal requirements which relate to inter alia themaximum acceleration that may occur in the centre of gravity of thebrain at a specified load. Typically, tests are performed, in which whatis known as a dummy skull equipped with a helmet is subjected to aradial blow towards the head. This has resulted in modem helmets havinggood energy-absorption capacity in the case of blows radially againstthe skull. Progress has also been made (e.g. WO 2001/045526 and WO2011/139224) in developing helmets to lessen the energy transmitted fromoblique blows (i.e. which combine both tangential and radialcomponents), by absorbing or dissipating rotation energy.

Such oblique impacts (in the absence of protection) result in bothtranslational acceleration and angular acceleration of the brain.Angular acceleration causes the brain to rotate within the skullcreating injuries on bodily elements connecting the brain to the skulland also to the brain itself.

Examples of rotational injuries include subdural haematomas (SDH),bleeding as a consequence of blood vessels rapturing, and diffuse axonalinjuries (DAI), which can be summarized as nerve fibres being overstretched as a consequence of high shear deformations in the braintissue.

Depending on the characteristics of the rotational force, such as theduration, amplitude and rate of increase, either SDH, DAI or acombination of these injuries can be suffered. Generally speaking, SDHoccur in the case of accelerations of short duration and greatamplitude, while DAI occur in the case of longer and more widespreadacceleration loads.

It has also been suggested to incorporate an airbag element intohelmets. In this context, and the context of this document moregenerally, the term ‘airbag’ is not used restrictively to be literallylimited to a bag filled with air. Rather, as in the automotive industry,the term is used to refer to an inflated or inflatable ‘cushion’,provided to protect a user in the event of an impact. For example, U.S.Pat. No. 6,418,564 discusses the possibility of providing an inflatablecollar around the lower perimeter of a helmet.

However, the prior art devices do not consider the affect of airbags onoblique impacts. The present invention aims to at least partiallyaddress this problem.

The invention is described below by way of non-limiting examples, withreference to the accompanying drawings, in which:

FIG. 1 is a diagram of a user wearing an airbag-equipped helmet, whereinthe airbag being of the dynamic type and uninflated;

FIG. 2 is a diagram of the user and helmet as in FIG. 1, but wherein theairbag is inflated;

FIG. 3 is a diagram of an inflated airbag, such as that of FIG. 2,undergoing an angled impact;

FIG. 4 is a diagram of a user wearing an airbag-equipped helmet, whereinthe airbag is of a pre-inflated variety;

FIG. 5A shows a plan view of the top of an airbag which is formed bycoiling a tube-shaped compartment;

FIG. 5B shows an airbag comprising individual compartments separated bywalls or membranes.

The present invention aims to provide an airbag-equipped helmet thatprovides increased protection when the helmet undergoes angled impact.By providing an airbag that has internal reinforcements, the airbag canbe optimised to reduce the rotational forces that would otherwise betransmitted to the head during an impact. Therefore, such a reinforcedor armoured airbag can provide increased protection against injury for auser wherein the airbag equipped helmet.

FIG. 1 depicts a cross-section of an airbag-equipped helmet 10 beingworn by a user 20. The helmet 10 may be of any type previouslymentioned, but in particularly preferred embodiments may be a bicycle ormotorcycle helmet.

The airbag 1 of the helmet 10 is not particularly limited in type. Inparticular, the term “airbag” is not intended to be interpreted to belimited solely to bags filled with air. Rather, as in the automotivesector, it is intended to refer to devices of the type which areinflated or inflatable to provide a cushion when a user undergoes animpact. As such, the airbag 1 may be filled by any suitable gas, whichmay or may not include air, or even a liquid if appropriate. Inparticular embodiments, the airbag 1 may be filled, or be designed to befilled predominantly with nitrogen.

Further, the airbag 1 may not be a single compartment or “bag”, but maybe formed of several interlinking or connected compartments.Alternatively, the airbag 1 may be formed by a single compartment butarranged in a folded or contorted configuration. For example, FIG. 5Ashows a plan view of the top of an airbag 1 which is formed by coiling atube-shaped compartment. FIG. 5B shows an airbag 1 comprising individualcompartments 51 separated by walls or membranes 50 (shown in the Figure,but internal to the airbag 1 in practice). The compartments 51 can beinterlinked, as shown, via openings 52 in the walls 50.

The material used to create the wall of the airbag 1 is not particularlylimited. Any suitable material can be used. For example, the airbag wallcan be made from nylon fabric. The fabric can be provided with anysuitable coatings or treatments. For example silicone or urethanecoatings can provide heat resistance

The airbag 1 shown in FIG. 1 is a “dynamic” airbag, meaning that theairbag 1 is uninflated until it is required i.e. it is only deployed toits ‘active’ state to provide protection in the event of an impact. Assuch, the helmet 10 is provided with a generator device 4, forgenerating the gas to inflate the airbag 1 when required. The gasgenerator 4 typically comprises chemicals that can be mixed together torapidly produce large amounts of the required gas, when triggered.Alternatively, the gas generator 4 could be a compressed gas cylinder,or any other suitable device for releasing gas to quickly to inflate theairbag 1 when the user 20 is undergoing an impact.

The generator 4 may also comprise a controller for detecting an imminentimpact. Such an arrangement is convenient, as the controller triggersthe release of the gas by the generator 4. However, the controller canbe positioned at any desired location on the helmet 10. The controllercan be any type of device that can detect an imminent impact and triggerthe generator 4 accordingly. For example, the controller can comprise anaccelerometer to detect sudden changes in the acceleration of a user'shead, which are indicative of an impact or imminent impact. In apreferred embodiment, the accelerometer is a microelectromechanicalsystems (MEMS) accelerometer.

Although the preceding discussion has focussed on the airbag 1 elementof the helmet 10, the helmet 10 may also comprise other protectiveelements (although, in some embodiments, the airbag 1 may be provided asthe sole protective element). In the example shown in FIG. 1, the helmet10 is provided with a further protective layer 3, which could help toreduce some or all of the radial force in an impact. Such a layer couldbe made of foam material like expanded polystyrene (EPS), expandedpolypropylene (EPP), polyurethane (PU) or strain rate sensitive foamssuch as marketed under the brand-names Poron™ and D3O™. Alternativelythe layer could be of the hard shell variety, made of any suitable hardpolymer material such as polycarbonate (PC), polyvinylchloride (PVC) oracrylonitrile butadiene styrene (ABS) for example. The protective layer3 could be part of the airbag 1 (i.e. the inner surface), or could be aseparate layer that is attached to the airbag 1.

In some arrangements, the protective layer 3 can comprise two or morelayers. In particular, the protective layer 3 may incorporate a slidinglayer for allowing rotation between other layers in protective layer 3,or between layer 3 and the user's head, or between layer 3 and theairbag 1. Such a sliding facilitator may be provided as a discrete layerof a low friction material, for example. Alternatively, the slidingfacilitator may be present as a low friction surface treatment on thesurface of another layer in the protective layer 3 or on the airbag 1.Such sliding facilitators are known from e.g. WO 2001/045526 and WO2011/139224, which are herein incorporated by reference in theirentirety.

FIG. 2 shows the helmet of FIG. 1 after the airbag 1 has been inflated.As such, it is more readily observed in FIG. 2 that the internal cavityof the airbag 1 is provided with reinforcements 2. The reinforcements 2extend through the internal cavity of the airbag 1. The reinforcement 2extend between different points on the airbag wall. Those points arepredominantly on opposite sides of the internal cavity when the airbag 1is inflated. At least some of the reinforcements 2 are held in tensionwhen the airbag 1 is inflated (and there is no external impact forceacting on the helmet).

In FIG. 2 the reinforcements 2 are shown as a network or web of fibresor threads. However, the nature of the reinforcements 2 is notparticularly limited. The reinforcements 2 could be provided, forexample, as membranes, beams or tubes extending between points withinthe airbag cavity.

The reinforcements 2 are arranged to reduce the rotational energy thatwould otherwise be transmitted to the head in the event of an impact onthe helmet 10. This is achieved by the reinforcements 2 controlling theway in which the outer surface of the airbag 1 deforms during an impact.In particular, the outer surface of the airbag 1 is controlled to deformin such a way that the rotational energy that would otherwise betransmitted to the head of the user 20 is minimised. This can beachieved, for example, by the reinforcements 2 controlling the outersurface of the airbag 1 to deform in a particular way and provide aparticular shape to the outer surface of the airbag 1. Put another way,the reinforcements 2 can limit the way in which the airbag 1 deforms sothat the airbag takes a shape during impact other than that which wouldbe taken in the absence of the reinforcements 2. By adjusting the shape,e.g. to be substantially flat in the region of impact, the motion of thehead of the user 20 with respect to the impact location can beencouraged to be translational rather than rotational. As a result, therotational acceleration experienced by the head of the user 20 isreduced.

For example, in FIG. 3, the airbag 1 is shown undergoing atangential/angled impact. Following the impact, some of thereinforcements 2′ remain in tension due to their arrangement within thecavity of the airbag, and may even undergo some stretch. Otherreinforcements 2″ do not remain in tension, and become flaccid orfloppy. The combination of the reinforcements 2′ in tension andreinforcements 2″ not in tension, control the shape of the outer surfaceof the airbag 1. In the example of FIG. 3, and as discussed above, theouter surface of the airbag becomes substantially flat, allowing for agreater possibility that the user's head slides with respect to theobject being impacted upon, as opposed to undergoing sudden angularacceleration. As such, the rotational energy transmitted to the user'shead is reduced.

The reinforcements 2 may also absorb some compression forces. As such,the arrangement of the reinforcements 2 may be optimised to also providean element of impact protection as well as reducing the likelihood ofbrain injuries via a reduction in the transmission of rotation energy.That is, even if the airbag 1 is involved in an impact so fast that theairbag 1 is bottomed out, the reinforcements 2 can provide someadditional protection.

To assist in increasing the likelihood of sliding during an impact, theouter surface of the airbag 1 can comprise or be treated with a lowfriction material, for example. Alternatively, the material of theairbag 1 itself can be a low friction material.

FIG. 4 depicts an alternative embodiment of an airbag-equipped helmet 10being worn by a user 20.

In this embodiment, the helmet 10 is provided with an airbag 1,comprising reinforcements 2, and optional further protective layers 3(arranged between the airbag and the user's head) as previouslydiscussed. However, in this arrangement the airbag is a “constant” or“pre-inflated” airbag. That is, the airbag is not provided with anytriggering and/or inflation mechanism. The airbag is simply inflatedbefore the user equips the helmet, and remains inflated whether or notthe user is involved in an impact.

As a result, the outer surface of the airbag can further comprise anadditional protective layer 5. Protective outer layer 5 can be of thehard shell variety, or could comprise further materials such ascompressive foams to provide impact protection. The outer protectivelayer 5 may be a single continuous layer, or may comprise separate zonesor cells which are individually attached to the airbag 1. In any case,the outer layer 5 still permits the deformation of the airbag 1 in thecase of an impact (i.e. through being relatively weak, or by beingprovided with suitable articulation to allow parts of the layer 5 tomove with respect to other parts).

An advantage of providing a constant or pre-filled airbag 1 is that thehelmet 10 is simpler to manufacture, and less likely to fail throughtechnological malfunction. Further, if the airbag 1 does fail, it willbe immediately noticed by the user. However, in some activities, theincreased size of a constant or pre-filled airbag helmet 10 may bedetrimental to the user's ability to participate in the relevantactivity due to the increased size of the helmet. As such, in thoseactivities, a dynamic airbag may be more appropriate.

The provision of the outer protective layer 5 also provides an advantagein terms of protecting the airbag from puncture. Such an advantage canalso be obtained by providing an outer layer on a dynamic airbag helmetsuch as shown in FIGS. 1-3, without inhibiting the ability of the airbag1 to deploy (e.g. because the layer either breaks apart or divides intosmaller parts in a predefined way when the airbag 1 is activated). Ineither case (i.e. for either a dynamic or constant airbag 1), having anairbag exposed as the outermost layer of the helmet runs the risk of thematerial of the outer wall of the airbag 1 being damaged by thesurroundings. For example, for a cycling helmet, the helmet 10 may bescratched by thorns or twigs when cycling through/near foliage. Suchdamage may not be enough to cause deployment of a dynamic airbag 1, butcould prevent the airbag 1 from operating correctly in the future (e.g.by puncturing the material of the airbag 1). As such, an outerprotective layer 5 mitigates against the risk of such damage, allowingthe airbag 1 to operate as intended in the event of an impact.

The outer protective layer 5 may also be provided with a slidingfacilitator so that the protective layer 5 can slide with respect to theoutside of the airbag 1. Where the layer 5 is provided as separatepieces or cells, each piece or cell may be provided with its own slidingfacilitator.

The above description is by way of example only. The skilled reader willappreciate that other embodiments are possible and covered by theattached claims.

1. A helmet comprising: an airbag having an airbag wall surrounding aninternal cavity; and one or more tensional reinforcements extendingthrough the internal cavity between different points on the airbag wall.2. A helmet according to claim 1, wherein the tensional reinforcementsare arranged to reduce the rotational energy that would otherwise betransmitted to the head in the event of an impact.
 3. A helmet accordingto claim 1, wherein the airbag is pre-inflated.
 4. A helmet according toclaim 3, further comprising an outer shell, provided radially outward ofthe airbag.
 5. A helmet according to claim 1, wherein the airbag is adynamic airbag that inflates in the event of an impact.
 6. A helmetaccording to claim 5, further comprising a pressurised gas canister orgas generator for providing gas to the internal cavity in the event ofan impact.
 7. A helmet according to claim 6, further comprising acontroller for detecting an impact or imminent impact and instigatingthe provision of gas from the pressurised gas canister or gas generatorto the internal cavity.
 8. A helmet according to claim 6, wherein thecontroller comprises an accelerometer, preferably amicroelectromechanical systems (MEMS) accelerometer, to detect an impactor imminent impact.
 9. A helmet according to claim 1, further comprisingan inner shell provided radially inwards of the airbag.
 10. A helmetaccording to claim 9, wherein the inner shell is a hard shell, or ismade from a foam material, optionally EPP or EPS, for absorbing some orall of the compressive force in an impact.
 11. A helmet according toclaim 9, further comprising a sliding facilitator provided between theinner shell and the airbag, to facilitate rotation between the airbagand the inner shell in the event of an oblique impact on the helmet. 12.A helmet according to claim 1, wherein the tensional reinforcements areflexible or stiff.
 13. A helmet according to claim 1, wherein thetensional reinforcements are threads, membranes, beams or tubes.
 14. Ahelmet according to claim 1, wherein the outermost airbag wall comprisesa material, or is treated, for facilitating sliding of the airbag withrespect to an object being impacted upon.
 15. A helmet according toclaim 1, wherein, in the event of an impact, the arrangement of thetensional reinforcements reduces the rotational energy that wouldotherwise be transmitted to the head of a wearer of the helmet, butallows for local compression of the airbag in the region impacted upon.